粤北诸广山南部同构造花岗岩的厘定及其与铀成矿作用关系

粤北诸广山岩体为印支-燕山期形成的多期多阶段复式岩体,其南部发育浅层次热隆伸展构造。本文根据该岩体密下水地区出露岩性的宏观韧性变形与镜下微观证据、岩石学特征及构造年代学约束,认为区内燕山期花岗岩为同构造侵位岩体,能为区域热隆伸展构造的形成与演化提供可靠的年代学约束,可准确限定热隆伸展构造活动的时间下限。研究表明,区域热隆伸展运动启动于燕山早期(~160 Ma),较前人利用中基性侵入脉岩限定的时限提早了约20 Ma;区域铀成矿时代从早期(~150 Ma)至晚期(~40 Ma)与区域伸展构造活动的时间具有高度耦合性,揭示出区域热隆伸展构造的形成与演化过程对区域铀成矿具有控制作用;同时,该期同构造花岗岩与构造前花岗岩的接触带是早期高温铀成矿的有利部位。

Determination of the Syn-tectonic Granite and its Relationship with Uranium Mineralization in Southern Zhuguang Granite,North Guangdong

The Zhuguang granite in northern Guangdong was a multi-stage complex pluton formed in Indosinian-Yanshanian period. The shallow thermal uplift extensional tectonic was developed in the south of the granite. Based on the macroscopic ductile deformation, microscopic evidence, petrological characteristics and geochronological constraints of the exposed lithology in Mixiashui area in the granite, the paper has holden that the Yanshanian granite in the area was a syn-tectonic emplaced granite, which could provide reliable geochronological constraints for the formation and evolution of regional thermal uplift extensional tectonic, and could accurately limit the time of thermal uplift extensional tectonic activity. The results has showed that the regional thermal uplift extension started in the early Yanshanian (~160 Ma), which was about 20 Ma earlier than the previous time limit of intermediate mafic dikes; The age of regional uranium mineralization changed from early (~150 Ma) to late stage (~40 Ma) was highly coupled with the time of regional extensional tectonics, which indicated that the formation and evolution of regional thermal uplift extensional tectonics could control the regional uranium mineralization; At the same time, the contact zone between syn-tectonic granite and pre-tectonic granite was a favorable location for early high temperature uranium deposits.